:root {
  --bg: #f0f2f5;
  --card: #ffffffee;
  --text: #111827;
  --muted: #6b7280;
  --primary: #60a5fa;
  --primary-strong: #3b82f6;
  --danger: #f87171;
  --radius: 16px;
  --shadow: 0 20px 40px rgba(2,6,23,.25);
}

body {
  font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
  background:
    radial-gradient(1200px 600px at 80% -10%, rgba(99,102,241,.25), transparent 60%),
    radial-gradient(900px 500px at -10% 100%, rgba(56,189,248,.20), transparent 60%),
    var(--bg);
  margin: 0;
  height: 100vh;
}

.login-card {
  width: 100%;
  max-width: 520px;           /* 카드 최대 폭 */
  padding: 36px;
  background: var(--card);
  border-radius: var(--radius);
  box-shadow: var(--shadow);
  text-align: center;
  margin: 0 auto;
}

h2 {
  margin: 0 0 18px 0;
  font-size: 24px;
  color: var(--primary);
}

#loginForm {
  display: grid;
  gap: 14px;
}

#loginForm input {
  width: 100%;
  padding: 14px 16px;
  border-radius: 12px;
  border: 1px solid rgba(148,163,184,.25);
  background: rgba(255,255,255,.06);
  color: var(--text);
  outline: none;
  transition: border-color .15s ease, box-shadow .15s ease, background .15s ease;
}
#loginForm input:focus {
  border-color: var(--primary);
  box-shadow: 0 0 0 3px rgba(99,102,241,.35);
  background: rgba(255,255,255,.10);
}

button[type="submit"] {
  width: 100%;
  padding: 14px 18px;
  border: 0;
  border-radius: 12px;
  background: linear-gradient(180deg, var(--primary), var(--primary-strong));
  color: white;
  font-weight: 600;
  letter-spacing: .2px;
  cursor: pointer;
  transition: transform .06s ease, filter .15s ease;
}
button[type="submit"]:hover { filter: brightness(1.05); }
button[type="submit"]:active { transform: translateY(1px); }

#message {
  margin-top: 10px;
  min-height: 18px;
  font-size: 13px;
  color: var(--danger);
  text-align: center;
  animation: fadeIn .25s ease;
}
@keyframes fadeIn {
  from { opacity: 0; transform: translateY(-2px); }
  to { opacity: 1; transform: translateY(0); }
}

/* 회원가입 버튼 */
.signup-container { margin-top: 12px; text-align: center; }
.signup-btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;    /* 아이콘 + 텍스트 중앙 정렬 */
  gap: 8px;
  padding: 12px 25px;
  background: var(--bg);
  color: var(--primary-strong);
  border-radius: 12px;
  font-weight: 600;
  text-decoration: none;
  box-shadow: 0 4px 10px rgba(0,0,0,0.1);
  transition: filter .15s ease, transform .15s ease;
  width: 100%;                /* 카드 안에서 균등 정렬 */
  box-sizing: border-box;
}
.signup-btn:hover { filter: brightness(1.05); transform: translateY(-1px); }
.signup-icon { width: 20px; height: 20px; }

/* 메인으로 돌아가기 버튼 */
.back-main-container { margin-top: 12px; text-align: center; }
.back-main-btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;    /* 아이콘 + 텍스트 중앙 정렬 */
  gap: 8px;
  padding: 12px 25px;
  background: var(--bg);
  color: var(--primary-strong);
  border-radius: 12px;
  font-weight: 600;
  text-decoration: none;
  box-shadow: 0 4px 10px rgba(0,0,0,0.1);
  transition: filter .15s ease, transform .15s ease;
  width: 100%;
  box-sizing: border-box;
}
.back-main-btn:hover { filter: brightness(1.05); transform: translateY(-1px); }
.home-icon { width: 20px; height: 20px; }

/* ===================== 반응형 ===================== */

/* 태블릿 (<=900px) */
@media (max-width: 900px){
  .login-card { max-width: 420px; padding: 30px; }
  h2 { font-size: 22px; }
  #loginForm input { padding: 12px 14px; font-size: 15px; }
  button[type="submit"] { padding: 12px 16px; font-size: 15px; }
  .signup-btn, .back-main-btn { font-size: 14px; }
}

/* 모바일 (<=600px) */
@media (max-width: 600px){
  body { padding: 0; } /* 모바일에서만 좌우 패딩 */
  .login-card { padding: 24px; border-radius: 12px; max-width: 95%; margin: 0 auto;}
  h2 { font-size: 20px; }
  #loginForm { gap: 12px; }
  #loginForm input { padding: 12px; border-radius: 10px; font-size: 14px; }
  button[type="submit"] { padding: 12px; border-radius: 10px; font-size: 14px; }
  .signup-btn, .back-main-btn { padding: 12px; font-size: 14px; }
}

/* 초소형 (<=400px) */
@media (max-width: 400px){
  .login-card { padding: 20px; }
  h2 { font-size: 18px; }
  #loginForm input { padding: 10px; font-size: 13px; }
  button[type="submit"] { padding: 10px; font-size: 13px; }
  .signup-btn, .back-main-btn { font-size: 13px; padding: 10px; gap: 6px; }
  .signup-icon, .home-icon { width: 18px; height: 18px; }
}

.login-container {
  display: flex;              /* 카드 정중앙 배치 */
  justify-content: center;
  align-items: center;
  height: 100%;               /* body 높이에 맞춤 */
  width: 100%;                /* 전체 폭 사용 */
}

/* 카드 자체 스타일 */
.login-card {
  width: 100%;
  max-width: 420px;           /* 카드 크기 제한 */
  margin: 0 16px;             /* 모바일 좌우 여백 */
}